Spectrum analyzers are commonly used to analyze the frequency spectra of electronic devices and components. Typically, the spectrum analyzer receives an input signal in the time domain, converts it to the frequency domain (e.g., by Fourier transform), and then displays the converted signal in a graph.
Unfortunately, certain types of signals may be difficult to measure and analyze in a conventional spectrum analyzer due to their irregular form. For example, frequency hopping signals, which are used in many communications applications, may be sparsely distributed in the frequency domain, making it difficult to display them with adequate time and/or frequency resolution.
Due to this difficulty, conventional approaches to analyzing frequency hopping signals tend to rely on compromises to simplify the analysis. For example, in one conventional approach, a spectrum analyzer examines frequency hopping signals with a wide instantaneous bandwidth. The use of a wide instantaneous bandwidth, however, limits the resolution and thus the visible details of the signals shape/modulation. Moreover, this problem increases as the bandwidth of the signal under test gets smaller compared to the entire hopping bandwidth.
In another conventional approach, a spectrum analyzer analyzes only a fraction of the signals occurring at one specific hop frequency. Analyzing only a fraction of a signal allows it to be analyzed with relatively high resolution. However, it increases the time needed to obtain an accurate measurement as only a tiny fraction of the entire signal is analyzed. Moreover, by not looking at the entire bandwidth it also makes it difficult to link specific effects to particular hopping patterns.
In yet another conventional approach, a device under test (DUT) is altered to avoid hopping (and a sparse use of the frequency domain). Turning off hopping, however, results in testing the DUT outside its normal operation and can thus only provide partial results.
In view of these and other shortcomings of conventional approaches, there is a general need for improved approaches for analyzing frequency hopping signals in spectrum analyzers.